1. Field of the Invention
The present invention relates generally to novel improvements in devices for mechanically and coherently amplifying the amount of sound wave radiation that is perceived by those with normal, unaided human ears. More particularly, it relates to such devices for mechanically directing these sound waves into one or both of the ears of a user in a manner that is both comfortable and that effectively recreates a phase-coherent, amplified image of the source of those sounds that the user faces. This invention also reduces the likelihood that onlookers will notice the device that produces this amplification when it is worn by a user. While prior art describes devices that can also reflectively increase the amount of sound received by the ears of users, none can perform this function with the unique combination of acoustic fidelity, comfort, reduced self-consciousness, and selectivity of the present invention.
Like other circumaurally-mounted oblate spherical lune or diangle-shaped paraboloid acoustic lenses, the present invention's roughly two-inch-diameter acoustic reflector effectively doubles the length of the user's ear canal by extending it. This increase helps to improve the user's perception of all sounds with a frequency of over 1.5 kilohertz, by cutting the resonant frequency of the ear canal in half. This increases the perceptibility of important frequencies in human speech (from 500 Hertz to 8 kilohertz) as well as musical fundamental notes as well as overtones. Further improvement to the volumes and coherence of the sounds amplified by the user's pinna as well as by the acoustic lens of the device are produced by using an obtuse angle at all points formed by the intersection of the transverse axis arcs of all sections of the lens at the line of its intersection with the head of the user.
Additionally and uniquely, the shape of the interior surface of the pliable material from which the invention is fabricated pushes against the top, rear, and bottom of the exterior of the pinna of the user's ear in order to move its rear face forward to form an obtuse angle to the head, and to hold the pinna fixed outward in this position. This increases the ability of the front, inner face of the user's pinna as well as a portion of the concha to reflect and focus sound radiated from sources in front of the user into the ear canal, as well as reflecting more focused sound from the inner face of the invention's lens. Since the pinna is known to serve as a directional collector and funnel for sound (for example, see http://en.wikibooks.org/wiki/Sensory_Neuroscience:_Hearing_and_speech/Outer_&_middle_ear/pinna), this repositioning improves the user's ability to identify the specific spatial positions of sound sources faced by the user. As noted on page 464 of the book Listening, by Stephen Handel (The MIT Press, 1989), “the pinna aids in front-to-back localization . . . [and its shape] creates a frequency filter so that as a sound source moves vertically from below the head to above the head, different frequency bands are accentuated and diminished. These changes provide localization information for elevation.”
2. Description of the Prior Art
The present invention's inventor noted the following in his previous patent covering a somewhat similar application of paraboloid acoustic lenses (U.S. Pat. No. 4,997,056):                “Researchers in related electroacoustic fields have identified such phenomena as sound wave phase incoherence and frequency group delays as causes for reduced information delivery by sound waves. Group delay causes a loss of natural realism to the perception of sounds, especially transients; in terms of measurements, group delay is plotted as the slope, or first derivative function of, phase shift versus frequency, showing the amount of time delay that is undergone by signal components in different segments of the frequency spectrum perceptible to humans. “Folded exponential horn” systems, such as described in Deutsches Reich Patentschrift Nr. 344526, issued Nov. 23, 1921 and U.S. Pat. No. 3,938,616, issued Feb. 17, 1976 to Brownfield, can cause sound waves to acquire these kinds of distortions, by causing excessive reflections and resonances within the amplifying device itself.        “Testing of active transducers (stereo headphones) used in close proximity to the ear has revealed that “ . . . sound pressure produced at the eardrum is critically dependant on the wave properties of the earphone and the external ear. The geometry of the cavities coupling the earphone to the ear drum, which is affected by such factors as the positioning of the earphone on the head of the listener, becomes the most critical issue [emphasis added]. These wave effects become important . . . at frequencies above about 2,000 Hertz . . . (sound pressures at the eardrum are) critically dependant on the geometry of the earphone and ear and the exact positioning of the earphone . . . .”; from a letter by Zwislocki, Kruger, Miller, Niemoeller, Shaw and Studebaker appearing in the April, 1988 issue of the Journal of the Acoustical Society of America.        
“A variety of additional hearing assistance devices and related structures are known in the art, which do not deal with the perceptible effects of the geometry of the invented device in relationship to the ear of the user. For example, hearing assistance devices including a cup configured for positioning behind and extending outward beyond the user's ear are shown in the following issued U.S. Pat. Nos. 1,708,257, issued Apr. 9, 1929 to Campbell; 1,820,107, issued Aug. 25, 1931 to Agee; 2,537,201, issued Jan. 9, 1951 to Amfitheatrof; U.S. Pat. No. 4,574,912, issued Mar. 11, 1986 to Fuss et al. Somewhat related structures in combination With eyeglasses are disclosed in U.S. Pat. No. 1,621,629, issued Mar. 27, 1927 to Dawson and U.S. Pat. No. 3,943,925, issued Mar. 16, 1976 to Leight. None of these prior art devices overcome the problems with such devices discussed above.”
What was implicit in the above statements but not noted in the claims cited for any patent before or since (including U.S. Pat. No. 4,997,056) is the need to form the pinna of the human ear into a more effective acoustic lens shape in order to enable the ear to naturally collect more radiated sounds. The use of the tissue of the ear for this purpose is inherently superior to the use of any other material, as will be noted by using one's hand cupped around one's ear, in a variety of positions and shapes, as a means of determining the optimum form for such a sound collector and concentrator. Given the characteristic shape of most human ears, a parabolic curve that forms an oblate lune or diangle portion of a sphere is likely to prove to be the most effective and comfortable shape for this novel acoustically reflective lens.
Subsequent patents of several devices designed to increase the perceived volume of sound sources, such as U.S. Pat. Nos. 5,345,512, 5,965,850, 6,082,486, and 6,237,714, all suggest the use of headband mountings to hold reflectors or lenses in place behind both ears of a user. U.S. Pat. No. 5,965,850 does call for using the headband's reflectors to position the user's pinna forward, but it does not use the reflector to induce an acoustic lens-shaped configuration in the positioning of the ear.
One other (apparently unpatented) product called “Serious Listeners” was briefly marketed in the mid-Nineties. This device used a pair of softly pliable, foldable leather reflectors to permit the user to use the product on one ear at a time; however, it did not provide lenticular accuracy to its reflections, nor did it permit the user to prop the pinna forward in optimum listening position.